1. Field of the Invention
This invention relates to an air dryer system for use in a compressed air system. More particularly, the invention relates to an air dryer system comprising a lithium chloride desiccant.
2. Discussion of the Art
Compressed air systems are widely used to operate a number of devices, and find particular use in braking systems for heavy vehicles. These systems include an air compressor which compresses ambient air and charges a storage reservoir. The compressor is engine operated and a governor, responsive to the reservoir pressure, selectively enables or disables the compressor as needed. Air dryers commonly employ a drying material or desiccant through which air passes to remove entrained moisture and limit problems related to moisture associated with brake system components. Moisture is adsorbed by the desiccant and removed from the compressed air before it is communicated to the storage reservoir. In these known systems, periodic or cyclic purging of the air dryers is required in order to purge or regenerate the desiccant.
Furthermore, in pneumatic systems such as those associated with trailer air dryers, the moisture in the air is often mixed with hydrocarbons. Low pH organic acids are formed which affect the various rubber components associated with the system. In addition, the hydrocarbons cause damage to the desiccants, and render them less productive. For example, desiccants comprised of molecular sieves, zeolites and silicas are oleophilic. As a result, air dryers associated with these desiccants are less effective and function at reduced efficiency. Entire desiccant cartridge assemblies are replaced on a periodic basis, often between about one and five years. There is a need for a desiccant useful in compressed air systems that tolerates oil and efficiently absorbs the moisture present in the compressed air that flows through a trailer air dryer.
The present invention solves the noted problems and others and provides an air dryer useful in a trailer braking and suspension system.
According to the invention, an air dryer for a trailer braking assembly comprises a housing having a passage extending therethrough for receiving air from a supply end and providing air to a delivery end. The passage is adopted for holding a drying material for removing moisture from the air. A drying material disposed in the passage includes a plurality of semi-rigid porous substrates impregnated with lithium chloride.
According to another aspect of the invention, an adsorbent desiccant for dehydrating moist gas by adsorption comprises a plurality of semi-rigid porous substrata carriers. Each carrier is impregnated with lithium chloride for removing moisture from the compressed air system.
According to another aspect of the invention, a desiccant for removing moisture from air in a compressed air system is formed by preparing a saturated solution of lithium chloride and a polar solvent. Porous substrata are contacted with the saturated solution to wet the substrata surface. The wet substrata are heated at a sufficient temperature for a sufficient duration to drive off excess solvent from the substrate. A desiccant comprising lithium chloride impregnated substrata is produced.
According to a still further aspect of the invention, there is a method of drying compressed air in a truck brake system. A desiccant comprising a plurality of lithium chloride impregnated semi-rigid porous substrata is packed in an air passage defined by an air dryer housing. Moist air is passed through the desiccant. Water vapor is removed from the moist air, and liquefied lithium chloride is retained on the porous substrate. Low humidity air is passed through the desiccant to remove water from the liquefied lithium chloride.
According to a yet still further aspect of this invention, there is a method for dehydrating a gas. A desiccant comprising lithium chloride on rigid porous substrata is placed into a container strong enough to withstand inlet gas pressure. Saturated inlet gas flows through the desiccant and water is adsorbed by the lithium chloride. Dried gas is passed through the desiccant to remove water from and regenerate the desiccant.
A primary benefit of the present invention is the ability for the desiccant in the trailer air dryer to remove moisture from the compressed air at a high capacity.
Still another benefit resides in the oleophobic nature of the desiccant employed in the trailer braking system which results in a longer lasting desiccant over molecular sieve, zeolite based silica or alumina based substrata.
Yet another benefit of the invention is realized by the ease with which the lithium chloride impregnated substrata are made.
Still other advantages and benefits of the invention will become apparent to those skilled in the art upon a reading and understanding of the following detailed description.